The present invention relates generally to aircraft, and more specifically the invention pertains to a missile airframe and high L/D wing design for the 2000 lb. class of air launched air-to-surface missile applications.
It is known that a substantial increase of the lift to drag ratio of an airfoil can be obtained by increasing the geometric aspect ratio of the wing system of the airfoil, since the induced drag decreases as the aspect ratio increases. With respect to air launched air-to-air missiles, improvements in the design of the fuselage, wings and fins can potentially provide extended standoff range as well as potential for low radar cross section, and low carriage drag. The increase in standoff range provides increased air craft survivability without reducing payload weight on target.
The task of providing a missile airframe and high L/D wing design with extended standoff range, low radar cross section and low carriage drag is alleviated, to some extent, by the systems disclosed in the following U.S. Patents, the disclosure of which are specifically incorporated by reference:
U.S. Pat. No. 2,074,099 issued to Adams; PA0 U.S. Pat. No. 2,643,076 issued to Hurel; PA0 U.S. Pat. No. 2,961,928 issued to Rosenthal; PA0 U.S. Pat. No. 3,020,986 issued to Kirk et al; PA0 U.S. Pat. No. 3,063,375 issued to Hawley et al; PA0 U.S. Pat. No. 3,145,000 issued to Mackie; PA0 U.S. Pat. No. 3,416,756 issued to Windecker; PA0 U.S. Pat. No. 3,567,407 issued to Yoblin; PA0 U.S. Pat. No. 4,000,871 issued to De Haai; and PA0 U.S. Pat. No. 4,471,923 issued to Hoppner et al.
The patent of Adams illustrates a fuselage of triangular shape formed by two upper longerons and a single lower longeron. A somewhat similar structure was used in the fuselage of an airplane produced during the late 1920s by the Fairchild company that incorporated two bottom longerons and a single top longeron. It gained the nick-name "Razorback".
The more recently issued patent to DeHaai discloses a high speed aircraft having a fuselage using two lower spaced apart tubular longerons and a single upper longeron. The use of high aspect ratio wings to achieve reduced drag is common practice in certain classes or aircraft such as sailplanes.
The reference Hurel suggests aspect ratios higher than 15 and possibly as high as 30, 40 or more can be used. The use of folding wings for projectiles or missiles is old as shown by the patents to Rosenthal and to Hoppner et al. The use of folding fins or tail surfaces on a missile is shown for example, by the reference Hawley et al. The remaining references Kirk et al, Mackie, Windecker and Yoblin all illustrate use of composite materials in aircraft construction.
While the above-cited references are instructive, the need remains to provide a missile design with the extended standoff range, low radar cross section, and low carriage drag features mentioned above. The present invention is intended to satisfy that need.